Semiconductor unit



106- 4 CROSS REFERENCE EXAMINER March 3, 1953 K. RAHBEK 2,630,512

SEMICONDUCTOR UNIT Filed Aug. 7, 1947 SEMICONDUCTOR UNIT Knud Rahbek,Frederiksberg, Denmark Application August 7, 1947, Serial No. 767,309 InDenmark February 27, I946 This invention relates to semi-conductor unitsfor the utilisation of electro-adhesion.

In the production of semi-conductor units for this purpose, it'hasappeared that natural semiconductors, such as agate, slate, soapstoneand others, suffer from the disadvantage that they are laminated andtherefore do not give a perfectly uniform effect independent of theirorientation. If, thus, in the semi-conductor unit a cylinder produced,for instance, of agate is being used and rotated in relation to a bandmade of an electrical conductor which is held pressed against itssurface, the tension caused in the longitudinal direction of the band byelectroadhesion'vary with the immediate position of the agate inrelation to the band, which may cause considerable trouble in the use ofthe unit.

The object of the present invention is to indicate a method"'for theproduction of artificial semi-conductors which are homogenous andtherefore do" not suffer from the said defect. Thisis attained by usinga unit consisting of a semi-conducting body composed of semi-conductingpowdery particles bound together by an electrically conducting bindingagent, a metallic electrical conductor contacting the surface of saidsemi-conducting body, means for moving said body and said conductorrelatively to each other along their contacting surfaces and means forapplying an electrical potentiaL. difference between the contactingsurfaces of said body and said conductor. y

Moulded pieces produced in this manner have proved to possess excellentsemi-conductor properties, and they may easily be given such mechanicalproperties as to make them suitable for use in the semi-conductor unitsin question. The production of artificial semi-conductors entails thefurther advantage, that the semi-conductor may easily be given the formsuitable for the purpose for which it is to be used, which isotherwiserather difficult, when for instance natural semi-conductors are used,which like agat'epossess very great hardness and therefore can be workedonly with difliculty.

Onthe drawing two examples of semi-conducting units in accordance withthe invention are shown in side elevation in Figs. 1 and 2 re-,spectively.

The unit shown in Fig. 1 consists of a rotatable metallic drum I, whichby means not shown can be rotated in direction of the arrow 2. Upon thecylindrical surface of the drum I a cylindrical layer -3 is fastened,which according to Section 1, Public Law 690, August 8, 1948 Patentexpires February 27, 1966 10 Claims. (01. 201-66) means of springs 5 and6 attached at oneoim their ends to the ends of the band 4 and fixed atthe other of their ends to holding means 1 and 8 in the apparatus, inwhich the unit is used. These means are only shown quitediagrammatically onthe drawing. The spring 6 attached to that end of theband 4 against which the layer 3 is rotating is a weak spring, whereasthe other spring 5 is more powerful. Between the metallic drum 1 and themetallicband 4 an electrical potential E is impressed as indicated onthe drawing.

Thelunit shown in Fig. 2 consists also of a metallic drum I, which can.be rotated in direction of the arrow 2. Against the cylindrical surfaceof this drum a semi-conducting band consisting of a layer 9 of powderyparticles bound together by an electrically conducting binding agent ona reinforcing wire netting I0 is pressed. Also this band is by means ofsprings 5 and 6 attached to its ends connected to holding means I and 8in the apparatus, in which the unit is used and an electrical potentialE is impressed between the metallic drum I and the band 9 as shown.

When the potential E is varied during the rota'tion of the drum I, theforce exerted by the spring 5 on the holding means I and the position ofthe band in relation to the holding means in both examples will in knownmanner vary in accordance with the variations of the potential.

By a suitable choice of the substances used in the production,semi-conductors possessing different properties, corresponding to thevarious uses to which they are to be put, may be produced. It has provedthat the powder used may be produced by pulverising naturalsemi-conductors, such as agate, slate, Solenhofen stone or %a gs tgn q,but also natural powders or im'neral pow ersin commercial use may beused, as for instance talc or flint powder.- As binding agent coagulentmineral substances, as for instance, water glass, may be used. It may bepointed out that flint powder stirred up in waterglass will make anartificial semi-conductor which is as hard as natural agate, and whichcan be out only with a diamond. Such an artificial semiconductorpossesses eminent properties as such. Likewise talc cast in water glasswill make an excellent semi-conductor. Both possess the advantage ofcoagulating slowly, so that the semithe inventign consists of powderyparticles bound 56 wnductors y j lly be formed, for instance in handswhen they are cast on wire netting. A semi-conductor produced of talc isto a certain extent self-lubricating, so that it will be especiallysuitable for units destined to be used in loudspeakers.

'- As bindin t may also be used coa ulent, organic su stances",especially substances containing cellulose or 'lastic substances whichin connection with even a hard powder may make a relatively softsemi-conductor.

As already mentioned in the foregoing and shown on Fig. 2 on the drawingthe mixture of powder and binding agent may prior to coagulation beplaced on reinforcing wires, preferably one or more wire nettings,whereby it will be possible to cast the semi-conductor in many differentforms, which may only with difliculty be obtained when naturalsemi-conductors are used.

The mass may also as shown in Fig. 1 be cast as a surface layer on abase formed in accordance with the purpose for which the semi-conductoris to be used. Such a base may preferably consist of metal, the surfaceof which has beforehand been made rough or rifled, so that the mass willhold securely onto the surface.

I claim:

1. A semi-conductor unit consisting of a semiconducting body composed ofsemi-conducting powdery particles bound together by an electricallyconducting binding agent, a metallic electrical conductor contacting thesurface of said semi-conducting body. means for moving said body andsaid conductor relatively to each other along their contacting surfacesand means for applying an electrical potential-diiference between thecontacting surfaces of said body and said conductor.

2. A semi-conductor unit as stated in claim 1 wherein thesemi-conducting body is built up of pulverized agate.

3. A semi-conductor unit as stated in claim 1 wherein thesemi-conducting body is built up of pulverized slate.

4. A semi-conductor unit as stated in claim 1 wherein thesemi-conducting body is built up of pulverized Solenhofer stone.

5. A semi-conductor unit as stated in claim 1 wherein thesemi-conducting body is built up of pulverized soapstone.

6. A semi-conductor unit as stated in claim 1 wherein thesemi-conducting body is built up of pulverized tale.

7. A semi-conductor unit as stated in claim 1 wherein thesemi-conducting body is built up of pulverized flint.

8. A semi-conductor unit as stated in claim 1 wherein thesemi-conducting body is built up by the said powdery particles beingbound together by water glass.

9. A semi-conductor unit as stated in claim 1 wherein the said powderyparticles are bound together by the said binding agent on areinforcement base.

10. A semi-conductor unit as stated in claim 1 REFERENCES CITED Thefollowing references are of record in the file of this patent;

UNITED STATES PATENTS Number Name Date 129,096 Brown July 16, 1872956,870 Wright et al May 13, 1910 1,393,346 Cook Oct. 11, 1921 1,533,757Rahbek et al. Apr. 14, 1925 1,638,849 Haverstick Aug. 16, 1927 1,638,888Slepian Aug. 16, 1927 1,883,675 Frank et al Oct. 18, 1932 1,973,732Snell Sept. 18, 1934 1,983,498 Lux Dec. 4, 1934 2,278,072 Gould et alMar. 31, 1942 FOREIGN PATENTS Number Country Date 503,218 Great BritainJune 30, 1937 I I y

